Related papers: Eta-Mesic Nucleus and COSY-GEM Data
$\eta NNN$ and $\eta NNNN$ bound states are explored in stochastic variational method (SVM) calculations within a pionless effective field theory (EFT) approach at leading order. The theoretical input consists of regulated $NN$ and $NNN$…
We suggest that the $\gamma p \to \phi \eta p$ reaction cross section, in the kinematics where the $\eta p$ invariant mass in the final state lies between the threshold value (m$_p$+m$_\eta$) and the N*(1535) resonance mass, is largely…
The WASA-at-COSY experiment has collected $3\times10^{7}$ events with $\eta$-mesons produced via the reaction $pd\rightarrow{^{3}\textrm{He}}\eta$ at $\textrm{T} = 1.0 \textrm{GeV}$. Using this data set, we evaluate the branching ratios of…
An exclusive measurement of the dd -> 3He n \pi 0 reaction was carried at a beam momentum of p = 1.2 GeV/c using the WASA-at-COSY facility. For the first time data on the total cross section as well as differential distributions were…
Measurements of the eta meson production with a polarised proton beam in the reaction p(pol) p --> p p eta have been carried out at an excess energy of Q = 40 MeV. The dependence of the analysing power A_y on the polar angle theta^*_q of…
We study the near-threshold photoproduction of $\eta^\prime$ mesons from nuclei in coincidence with forward going protons in the kinematical conditions of the Crystal Barrel/TAPS experiment, recently performed at ELSA. The calculations have…
It is argued that the strong energy dependence of the $p\, d \rightarrow \,^{3\!}H\!e\, \eta$ cross section near threshold is due to a final state interaction between the $\eta$ meson and the $^3$He nucleus. The large scattering length that…
We demonstrate that one can use the occurrence of charge symmetry breaking as a tool to explore the eta--nucleus interaction near the eta threshold. Based on indications that the cross section ratio of pi+ and pi0 production on nuclei…
The excitation function and momentum distribution of $\eta^\prime$ mesons have been measured in photon induced reactions on $^{12}{}$C in the energy range of 1250-2600 MeV. The experiment was performed with tagged photon beams from the ELSA…
The existing and some preliminary experimental data on the total cross sections of the $^{4,6}$He, $^{6,7}$Li +$^{28}$Si reactions at energies E=5-50 A MeV are demonstrated. The data on $^{6}$Li,$^{6}$He+$^{28}$Si are analyzed in the…
A high statistics measurement of the pp --> ppeta reaction at an excess energy of Q = 15.5 MeV has been performed at the internal beam facility COSY-11. The stochastically cooled proton beam and the used detection system allowed to…
The structure of eta-nucleus bound systems (eta mesic nuclei) is investigated as one of the tools to study in-medium properties of the N(1535) (N^*) resonance by using the chiral doublet model to incorporate the medium effects of the N^*…
The COSY-11 collaboration has measured the total cross section for the pp --> pp eta-prime and pp --> pp eta reactions in the excess energy range from Q = 1.5 MeV to Q = 23.6 MeV and from Q = 0.5 MeV to Q = 5.4 MeV, respectively.…
Coherent $\eta$ meson photoproduction on $^4$He and $^{12}$C is considered in the near-threshold region. The elementary $\eta$ photoproduction operator includes contributions from the $S_{11}(1535)$ and $D_{13}(1520)$ resonances as well as…
The recently discovered enhancement of eta photoproduction on the quasi-free neutron at energies around s^1/2 ~ 1.67 GeV is addressed within an SU(3) coupled channels model. The K Sigma threshold plays a significant role and the quasi-free…
The nuclear states of \bar K and \eta are bound by a similar mechanism - the excitations of nucleons to \Lambda (1405) and N*(1535) resonant states. The observed large differences in binding energies are understood in terms of separation of…
We study near-threshold $\eta$ meson production in $pp$ collisions within an effective Lagrangian approach combined with the isobar model, by allowing for the various intermediate nucleon resonances due to the $\pi$, $\eta$, and…
The existence of etamesic nuclei has been speculated for a long time without firm experimental evidence. Much of the effort has taken place in final state interactions on production. One crucial factor in seeing a quasibound state is its…
The resonance and bound--state poles of the amplitude describing elastic scattering of $\eta$-meson off the light nuclei $^2H$,\,$^3H$,\, $^3He$, and $^4He$ are calculated in the framework of a microscopic approach based on few--body…
The 28Si(p, p' gamma)24Mg reaction has been studied at the ITEP accelerator by the hadron-gamma coincidence method for a proton energy of 1 GeV. Two reaction products are detected: a 1368.6-keV gamma-ray photon accompanying the transition…